1. Field of the Invention
The invention relates to a steering system that includes a pinion shaft, a rack shaft and a support yoke.
2. Discussion of Background
A rack-and-pinion steering system includes a pinion shaft, a rack shaft and a rack guide mechanism. The pinion shaft has a plurality of pinion teeth. The rack shaft has a plurality of rack teeth. US 2008/0223163 A1 describes a steering system that includes a pinion shaft and a rack shaft,
The rack guide mechanism includes a support yoke, an urging member and a restricting member. The support yoke guides movement of the rack shaft. The urging member applies, to the support yoke, a force that acts in an urging direction that is a direction in which the support yoke is pressed against the rack shaft. The restricting member is located on the side of the support yoke and the urging member in an anti-urging direction, which is a direction opposite to the urging direction. The restricting member faces, via a clearance, an end portion of the support yoke in the anti-urging direction.
The steering feel is influenced by the magnitude of rotational resistance against the pinion shaft in the steering system. The magnitude of rotational resistance against the pinion shaft changes on the basis of the magnitude of reaction force that the pinion shaft receives from the rack shaft due to meshing between the pinion teeth and the rack teeth.
The magnitude of reaction force changes on the basis of a force that is applied from the urging member to the rack shaft via the support yoke. The magnitude of force that is applied from the urging member to the support yoke changes on the basis of the size of the clearance between the end portion of the support yoke in the anti-urging direction and the restricting member. Therefore, by controlling the size of the clearance between the end portion of the support yoke in the anti-urging direction and the restricting member, it is possible to adjust the magnitude of rotational resistance against the pinion shaft and the steering feel.
In the above-described steering system, when the pinion shaft rotates, the rack shaft receives a force in the anti-urging direction due to the meshing between the rack teeth and the pinion teeth. Therefore, the rack teeth are separated from the pinion teeth. The rack teeth, which have been separated from the pinion teeth, contact the pinion teeth again due to the action of a force that is applied from the urging member to the rack shaft via the support yoke. Then, gear rattle is generated when the rack teeth contact the pinion teeth.
Therefore, it is desirable to take measures for suppressing generation of such gear rattle. However, the steering system is required to provide good steering feel. Therefore, when the above-described measures are taken, it is desirable to take into account the influence on the steering feel.